Nema 17 Stepper Motor Bipolar L=38mm w/ Gear Ratio 27:1 Planetary GearboxDon't look to be swapping gearboxes, or maybe you can in the right configurations, dunno. The shaft on the motor is splined to work directly as the sun gear on the planetary gear box. I was hoping to see a D shaft in there to make it more useful in any configuration. The existing makes sense, just not what I was hoping for.RAT 14/06/2017